1. Field of Invention
The invention relates to a cleaning patch and method thereof for cleaning a toner. More explicitly, the invention pertains to a cleaning patch and method thereof for cleaning a residual toner in a developing unit.
2. Related Art
Electrophotographic image systems utilize the principle of ElectroPhotoGraphy (EPG) to print images. The EPG involves several steps: charging, exposure, developing, transferring, and fusing.
When the image forming device prints an image, a high-voltage corona charging unit distributes negative charges all over the surface of a photoreceptor. This is the charging step. In the exposure step, the image to be printed is converted into an optical signal and irradiated using a light-emitting diode (LED) or a laser on the photoreceptor that is already charged with negative charges. The irradiated region has a higher potential than the un-irradiated region. Such a potential difference is used to represent the potential image, also called the latent image.
The developing step starts right after the required latent image is formed on the photoreceptor. The developing unit has the toners with the same potential as the un-exposed region. The toners cannot adhere onto the un-exposed region due to the repulsive electrostatic force. However, they are attracted to the exposed region with a higher potential. Therefore, the exposed region is disposed with toners.
Once the developing step is finished, the toners adhered on the photoreceptor are transferred to paper. This is the transferring step. In this step, a transfer roller is used to distribute positive charges on the back of the paper. Thus, the toners on the photoreceptor are transferred onto the paper. Finally, a heat roller and a pressure roller are used to fix the toners on the paper. This is the fusing step. A cleaning station then cleans the cleaning patch on the photoreceptor after transferring step.
In order to prevent the residual toners from a previous developing from affecting the current developing, the photoreceptor can be provided with a cleaning patch during the developing step, as disclosed in U.S. Pat. No. 6,687,473. That patent only discloses the idea of effectively removing possible residual toners in order not to pollute the developing step, thus improving the image quality. It does not explicitly disclose the implementation method.
Therefore, it is imperative to provide a method that can evenly distribute residual toners on a cleaning patch in order not to pollute the developing step and increase the efficiency of the cleaning station to remove the toner from the photoreceptor.